An obvious problem is how to protect the operator of a small boat or so-called personal water craft, when the person is alone, if the person falls overboard into the water while the boat engine is propelling the boat. The boat can continue to run on its course, leaving the operator alone in the water and in jeopardy, especially when the boat is distant from land or other boats.
A common means for protecting the operator in the prior art is as follows. A tether or lanyard runs from the operator's belt or other attachment to a plastic mechanical clip, familiarly called a “key”, which slips onto the outside of a kill switch of the boat engine. The kill switch is typically located on the control or instrument panel of the boat. It has a movable spring-loaded part which has to be held in a certain position for the boat to run. As shown in FIG. 1, such key 40 which works with the spring loaded portion of the switch is distinguished from a metal turn key 34 which turns within the switch. Hereinafter, such key 40 is referred to as a latch key. When the operator falls overboard the lanyard tensions and pulls the latch key for the switch. The spring action within the kill switch breaks the electric circuit of the engine ignition system, turning off, or “killing” the engine. Taskahsima U.S. Pat. No. 6,352,045 describes a kill switch and engine control system of such type. The presumption is that the operator can swim back to stopped boat.
The disadvantage of such prevalent type of commercial system is that use of a lanyard, although simple, inhibits the normal movement of the operator and such other persons as may be on the watercraft. The kill switch can be inadvertently tripped by the operator when he or she moves about normally, or when the operator strays too far from the switch location but has not fallen overboard. Many boat operators and occupants regard the device as a nuisance and something that “gets in the way”. As a result, oftentimes the operator does not fasten the lanyard to his or her person, thus defeating the goal of providing safety. It is not uncommon to view boats in operation, with the lanyard dangling down the instrument panel from the switch, and running to nothing. Also, the present system can't protect against a person other than the operator from falling overboard.
Other inventors have attacked the problem of providing protection in a less inconvenient way. For example, Simms U.S. Pat. No. 4,305,143 describes the essential problem of “man-overboard”. See also the Murray patent, mentioned below. Simms describes an ultrasound device which is activated by a hydrostatic switch, which in turn is activated by contact with the water with which the boat operator contacts upon falling overboard. The ultrasound unit that responds to the signal is contained within the control circuit of the engine, separate from the kill switch. Boe U.S. Pat. No. 4,714,914 describes how immersion in water triggers a radio signal from a device worn by the operator. The signal causes various optional things to happen, including causing a solenoid valve to shut off the fuel to engine. Morgan U.S. Pat. No. 5,021,765 describes a unit comprised of a dual receiver radio signal system. Activation when the operator falls overboard causes an alarm to sound at the boat, or causes ejection of a life buoy into the water. Guldbrand U.S. Pat. No. 5,945,912 describes a system having a transmitter carried by the operator, which transmitter floats. When the operator falls overboard, the transmitter signals a receiver on the boat. That causes actions on the boat, including optionally the activation of a kill switch or lowering of the sails. Murray U.S. Pat. No. 5,838,227 describes a radio receiver that has been wired into the engine control circuit. When a signal to the receiver from a radio transmitter carried by the operator falls below a threshold level, the receiver causes the engine to stop or takes other pre-programmed action.
While lanyard-free systems of the type mentioned above may serve the intended purpose, they have not found wide commercial use. From inquiry and observation, the reasons appear to include: that the prior art devices lack essential simplicity and low cost of the lanyard system; that they have to be either installed at the factory, or inconveniently in the field by a skilled electrician; and, that it is difficult to adapt hard-wired systems to the diversity of boat instrument panel and wiring configurations. Thus, there is a continuing need for improvement in addressing the problem.
Analogous problems are presented by land vehicles, such as motorcycles, particularly those used in racing, and by snowmobiles, where is it bad for the vehicle to keep running when the operator falls off.